The present invention is directed to a conference circuit of the type using a comparison between the loudness of speech samples derived from parties to the conference during each frame to transmit the speech of the loudest party to the other parties to the conference. The conference is designed for use in a system using time division switching in which a plurality of multiple party conferences may be in operation simultaneously under the control of the conference circuit. Such conference circuits are shown generally by U.S. Pat. No. 4,022,981 issued May 10, 1977 to D. W. McLaughlin et al, and by U.S. Pat. No. 3,699,264 issued Oct. 17, 1972 to S. Pitroda et al.
The present circuit is designed for use on a small PBX, key system of the type shown generally by co-pending application Ser. No. 135,464 filed Mar. 31, 1980 and Ser. No. 194,209 filed Oct. 6, 1980, now U.S. Pat. No. 4,339,633 issued July 13, 1982 to F. Ahmed, and in the application of W. Williams and myself, Ser. No. 225,020, filed on the same day as the present application. The circuit of the present invention is directed to a smaller capacity system than that shown by the cited Ahmed applications, using only one processor for controlling call completion in the system.